Determination of the substrate-docking site of protein tyrosine kinase C-terminal Src kinase

Authors

Sungsoo Lee, University of Rhode Island
Xiaofeng Lin, University of Rhode Island
Nguyen Hai Nam, University of Rhode Island
Keykavous Parang, University of Rhode Island
Gongqin Sun, University of Rhode Island

Document Type

Article

Date of Original Version

2003

Department

Cell & Molecular Biology

Abstract

Protein tyrosine kinases (PTK) are key enzymes of mammalian signal transduction. For the fidelity of signal transduction, each PTK phosphorylates only one or a few proteins on specific Tyr residues. Substrate specificity is thought to be mediated by PTK–substrate docking interactions and recognition of the phosphorylation site sequence by the kinase active site. However, a substrate-docking site has not been determined on any PTK. C-terminal Src kinase (Csk) is a PTK that specifically phosphorylates Src family kinases on a C-terminal Tyr. In this study, by sequence alignment and site-specific mutagenesis, we located a substrate-docking site on Csk. Mutations in the docking site disabled Csk to phosphorylate, regulate, and complex with Src but only moderately affected its general kinase activity. A peptide mimicking the docking site potently inhibited (IC₅₀ = 21 μM) Csk phosphorylation of Src but only moderately inhibited (IC₅₀ = 422 μM) its general kinase activity. Determination of the substrate-docking site provides the structural basis of substrate specificity in Csk and a model for understanding substrate specificity in other PTKs.

Citation/Publisher Attribution

Lee, S., Lin, X., Nam, N. H., Parang, K., & Sun, G. (2003). Determination of the substrate-docking site of protein tyrosine kinase C-terminal Src kinase. Proceedings of the National Academy of Sciences, 100(25), 14707-14712. doi: 10.1073/pnas.2534493100

Available at: https://doi.org/10.1073/pnas.2534493100

Comment

Sungsoo Lee and Xiaofeng Lin are in the Department of Cell and Molecular Biology. Nguyen Hai Nam and Keykavous Parang are in the Department of Biomedical Sciences in the College of Pharmacy. And Gongqin Sun has a dual appointment with both departments.